Nuclear Transmutation

Nuclear transmutation is the conversion of one element into another, which is possible via radioactive decay, nuclear fusion, and nuclear fission.

Additionally, Ernest Rutherford demonstrated that nitrogen-14, when hit with a fast-moving alpha particle, produces a proton along with a different nuclide, which, a few years later, was identified as oxygen-17 by Patrick Blackett. 

The condensed notation of the process lists, in order, the target nucleus, the bombarding and ejected particles, and the product nucleus. Neutrons and alpha particles are common bombarding particles in transmutation processes. 

The elements with atomic numbers greater than 92 are called transuranium elements. These elements are common targets of transmutation experiments because they are entirely synthetic except for neptunium and plutonium, which are also produced naturally in uranium decay chains.

For example, neptunium-239 is generated in specialized nuclear reactors by bombarding uranium-238 with fission neutrons. Being electrically neutral, neutrons encounter no electrostatic repulsion from the nuclei, so fission speeds are sufficient for this transmutation. The radioactive neptunium-239 subsequently decays into plutonium-239. 

In further experiments, plutonium-239 is hit with high-speed alpha particles to yield curium, which has an atomic number of 96. Unlike neutrons, alpha particles must overcome electrostatic repulsion exerted by the positively charged target nuclei and thus require greater kinetic energy.

Notably, the electrostatic repulsion is greater with larger nuclei like plutonium-239 than with smaller nuclei like the nitrogen-14 used in the Rutherford and Blackett experiments.

Particle accelerators, which include linear accelerators and cyclotrons, impart the desired high speeds to charged nuclear particles.

A multistage linear accelerator has a series of tubes of increasing lengths and alternating polarities. An oscillating electrical potential rapidly switches the polarities so that the charged particles are alternately attracted and repelled by each tube.

The particle accelerates as the tubes get longer, ultimately reaching speeds that can exceed 90% of the speed of light. In a cyclotron, alternating voltage instead accelerates the particle in a spiral path.

Particle accelerators can bombard nuclei even with other relatively large nuclei, like bombardment of lead-208 with a beam of zinc-70. The product transuranium element, copernicium-277, generates thirteen transuranium elements through its major decay chain, which eventually leads to bismuth-209.